This invention relates to antennas in general and more particularly to an antenna for radiating high frequency electromagnetic energy such that the energy is confined to form a highly directional beam.
In U.S. Pat. No. 3,721,988 a leaky wave guide planar array antenna is disclosed. This planar array produces four squinted beams used for an airborne doppler navigation system. The antenna includes a pair of slotted feed rectangular wave guides arranged to permit input energy to be applied at any one of four ports. Interconnecting and coupled to the feed wave guides by means of slots and feed wave guides is a radiating member which includes a leaky grid structure through which beam forming electro-magnetic energy is radiated. In that arrangement, each port into one of the slotted arrays is used to generate a single beam. Clearly where only one or two beams are required the same technique can be used.
Although that antenna operates quite well and provides a low cost approach, it suffers from one disadvantage. The antenna is a planer array and if it were to be used as a conformal antenna for use as a tracking systm on missiles and artillery shells, or the like it, would require a conformal radome.
Clearly in such applications i.e., for use with tracking systems on missiles and artillery shells, there is a need for a low cost conformal antenna. Direct application of the antenna disclosed in U.S. Pat. No. 3,721,988 would increase the cost because of the need for the extra conformal radome. One approach to constructing a conformal wave guide would be to use a slotted wave guide planar array such as that disclosed in U.S. Pat. No. 3,276,026. However in using such an array curved slotted wave guides must be used. It is well known that such a curved array requires a phase synthesis technique in its design. Typically such has been accomplished in the prior art through the use of active phase elements.
Other applications require a conformal antenna array which generates a pencil beam. Again such a conformal array will have curved surfaces and will require a phase synthesis technique in designing to obtain the desired output beam. Typically such an array may be desired in a spherical configuration.
In view of this it becomes evident that there is a need for an improved technique for constructing antennas which utilize curved wave guides, in particular those using slotted wave guides which avoids the need for active phase elements thereby permitting a simpler antenna construction in a conformal configuration.